(i) Field of the Invention
This invention relates to the treatment of sewage sludge-derived oils for the significant abatement of odours to allow for acceptability of utilization.
(ii) Description of the Prior Art
Sewage sludge-derived oil may be produced according to the teachings of Canadian Patent No. 1,225,062 issued Aug. 4th, 1987 to T. R. Bridle, contents of which being incorporated herein by reference. The teachings of such a patent may, however, be summarized as follows.
A batch-type reaction system for the production of such sludge-derived oil described in the above-identified Canadian patent may be operated as follows: A single reactor provides both heating and reaction zones and consists of a PYREX.TM. tube. This was heated in a furnace, off-gases being condensed in a trapping system consisting of three flasks connected in series, using ice as the coolant. Non-condensable gases (NCG) were vented by pipe from the system to a furnace hood and were not collected. A typical run was conducted by charging 550 g of dried sludge (93-96% solids) into the reactor and deaerating with nitrogen while in the vertical position. The reactor volumetric packing for all runs was a nominal 50%. The reactor was then placed in the furnace, which was inclined by a support 10.degree. to facilitate liquid transport. All the lines, traps, etc. were connected and the entire system purged with nitrogen (15 mL/s) for 20 to 30 minutes. The furnace was then switched on and brought up to operating temperature at a controlled rate, the control employing a thermocouple placed in the sludge bed and connected to thermocouple switch and readout. Once operating temperature had been reached, the nitrogen purge rate was reduced to 7 mL/s. When all visible signs of reaction, i.e., gas/oil flow, ceased the heat was switched off and the nitrogen purge rate increased to 15 mL/s for approximately 30 minutes. The system was dismantled and the char, oil and pyrolytic water collected and stored for analyses, oil/water separation being achieved using a separatory funnel.
The operating conditions and results for a continuous-type reactor system are shown in Table 1 below, while typical elemental analyses of the resultant oils and chars are shown in Table 2 and a distribution analysis of aliphatic hydrocarbons found in an oil is shown in Table 3. The continuous reactor results are shown in Table 4. All the data in the tables is expressed on a total solids basis (not corrected for volatiles). The non-condensable gas (NCG) yield was calculated by difference. Analysis of the NCG, by gas chromatography (GC), indicated that it contained roughly 6% methane and 10% carbon monoxide with the remainder comprising mostly carbon dioxide and nitrogen. The calculated calorific value is approximately 2.0 MJ/kg of NCG.
Most of the test runs were conducted at optimum conditions defined as: optimum conversion temperature as determined by differential scanning calorimetry; linear increase of temperature with time to operating temperature at 10.degree. C/minute; and continuous nitrogen purge. Runs 11, 12, 13, 22, 24 and 19 instead were conducted with one variable altered during each test, as indicated in Table 1.
TABLE 1 __________________________________________________________________________ TEST RUN CONDITIONS AND RESULTS __________________________________________________________________________ OIL OPERATING CONDITIONS CALORIC SLUDGE TEMP OTHER YIELD VALUE VISCOSITY RUN NO. SAMPLE (.degree.C.) COMMENTS % MJ/kg CENTISTOKES __________________________________________________________________________ 1,20,29 C 400 Optimum 20.8 36.40 Solid 5-10 D 450 Optimum 21.1 37.43 31.1 14,15,16 B 450 Optimum 24.1 33.13 60.5 2 C 425 63% WAS 25.8 33.83 70.3 3 C 425 75% WAS 28.6 34.13 97.5 4 C 425 88% WAS 28.7 31.77 214.0 11,12,13 B 350 Low Temperature 12.8 33.32 Solid 22 C 450 High Temperature 22.3 38.87 Solid 23 C 400 No N.sub.2 purge during run 19.8 38.00 44.9 24 C 400 Ramp at 5 C./min. 16.3 37.92 Solid 19 C 400 10000 ppm Ni spike 20.9 33.98 63.4 31 C 400 Second reactor, empty 19.0 37.49 Solid 32 C 400 Second reactor, char 17.2 38.18 39.5 33 C 400 Second reactor, catalyst 19.0 37.49 31.0 __________________________________________________________________________ RESULTS CHAR RUN NONCONDEN- PYROLYTIC CALORIC SABLES WATER THERMAL YIELD VALUE YIELD YIELD EFFICIENCY RUN NO. % MJ/kg % % % __________________________________________________________________________ 1,20,29 59.5 9.86 11.6 8.1 81.9 5-10 52.5 10.68 13.2 13.1 77.7 14,15,16 53.7 10.08 13.3 8.8 83.2 2 57.1 11.35 12.2 4.9 87.2 3 56.7 11.63 10.1 4.6 90.8 4 54.6 10.65 8.9 7.8 82.4 11,12,13 65.6 12.00 10.3 11.2 79.3 22 54.6 9.39 12.1 11.0 80.4 23 59.1 10.51 12.2 8.9 80.1 24 62.7 11.24 10.3 10.7 76.9 19 60.8 NA 10.6 7.7 88.7 31 60.0 11.07 12.0 9.0 80.1 32 59.9 11.07 13.0 9.9 77.0 33 56.8 10.01 14.8 9.4 75.0 __________________________________________________________________________ NA = Not Available *Solid defined as 214 centistokes .sup.+ Measured at room temperature (20-25.degree. C.) of Table 5 measurement at 38.degree. C. (ASTM standard)
TABLE 2 __________________________________________________________________________ OIL AND CHAR ELEMENTAL ANALYSIS (%) OIL CHAR Run No. C H N S O C H N S O __________________________________________________________________________ 20 78.00 10.10 3.99 0.75 6.18 25.45 1.97 2.79 1.39 11.90 9 78.74 10.17 3.45 0.41 6.37 26.02 1.61 3.01 1.16 12.70 15 77.39 9.70 4.95 0.83 6.90 24.53 1.22 2.84 0.74 9.26 22 77.92 10.20 3.99 0.61 6.51 22.53 1.34 2.54 1.52 12.54 23 78.00 10.30 3.42 0.74 7.00 23.83 1.70 2.59 1.44 11.55 24 77.91 10.44 3.87 0.74 6.48 24.76 1.85 2.83 1.33 12.37 19 79.07 10.06 4.66 0.53 7.07 23.36 1.56 2.76 1.48 13.25 31 76.92 10.15 4.11 0.65 6.89 26.53 2.13 2.80 1.31 11.94 32 79.76 10.25 4.19 0.56 5.84 25.97 1.98 2.80 1.34 11.63 33 79.30 10.41 3.49 0.34 5.84 24.22 1.62 2.74 1.50 11.35 __________________________________________________________________________
TABLE 3 ______________________________________ ALIPHATIC HYDROCARBON DISTRIBUTION IN OIL Compound % ______________________________________ C.sub.10 8 C.sub.10-15 30 C.sub.15-16 6 C.sub.16-17 5 C.sub.17-19 10 C.sub.19-20 10 C.sub.20-21 10 C.sub.21 21 100 ______________________________________
TABLE 4 __________________________________________________________________________ CONTINUOUS REACTOR RESULTS __________________________________________________________________________ REACTOR CONDITIONS Sludge Solids Char OIL Run Temp Fd Rt Residence Inv. Gas Gas Yield Cal. No. (.degree.) (g/h) Time (Min) (g) Seal Path (%) Value Viscosity __________________________________________________________________________ 34 350 750 8 51 no mixed 18.53 27.88 160 flow 35 450 750 8 54 no mixed 29.71 31.12 flow 36 500 750 8 53 no mixed 28.16 34.01 flow 37 450 750 28 201 yes counter 24.10 35.53 current 38 450 750 8 56 no 1st zone 24.46 30.06 only 39 450 750 8 55 no co- 27.96 33.20 current 40 450 1000 8 70 yes counter 26.75 31.04 current 41 450 500 20 88 yes counter 23.74 35.00 current __________________________________________________________________________ NOG CHAR Phys. Run Yield Cal. Yield Cal. Water Thermal Char In No. (%) Value (%) Value Yield (%) Effic'y SFR __________________________________________________________________________ 34 64.68 8.84 7.28 3.18 3.62 73.85 0.068 35 72 59.76 8.27 7.57 5.04 2.18 96.80 0.072 36 34 58.10 7.67 3.61 20.05 3.06 98.04 0.071 37 33 59.50 8.28 6.37 9.68 5.72 93.77 0.268 38 110 59.47 8.25 9.26 3.72 4.23 83.75 0.075 39 73 59.74 8.70 6.67 6.07 5.60 98.91 0.073 40 82 61.11 8.54 4.76 7.20 3.37 92.14 0.070 41 34 57.79 8.12 7.42 10.96 5.88 91.82 0.176 __________________________________________________________________________ Measured at 38.degree. C. (ASTM standard) of Table 1 measurement at room temperature Conducted using sludge from source "C
The sewage sludge-derived oil produced appears to be largely aliphatic with a moderate oxygen content but with nitrogen derived from proteins and fatty acid in the sewage sludge. The solid residue is 80% inorganic matter.
The above-described sewage sludge-derived oils may have the following composition:
______________________________________ General Range Typical Range ______________________________________ Nitrogen: about 2% to about 8% about 3.4% to about 5% Oxygen: about 3% to about 12% about 5.8% to about 6.9% Sulphur: about 0.1% to about 4% about 0.3% to about 0.8% Hydrogen: about 8% to about 11% about 9.7% to about 10.4% Carbon: about 86.9% to about about 76.9% to about 65% 79.8% ______________________________________
These sewage sludge-derived oils can be dehydrated by distillation. Portions of the nitrogenous groups appear to be amines and amides with some pyridinic and pyrrolic types. Portions of the oxygen-containing groups appear to be carboxylic and amide types.
The following Table provides an identification of individual components of sewage sludge-derived oil (SDO) by Gas Chromatography (GC)mass Spectrograph (MS):
______________________________________ Approximate Approximate concentration concentration in dehydrated sewage Components in Fraction sludge-derived oil ______________________________________ Fraction 1 (boiling: up to 176.degree. C.) (4.6% of dehydrated sewage sludge-derived oil) Low boiling aromatics 15.3% 0.7% Pyridines 1.1% 0.05% Total Alkanes 2.5% 0.12% Indoles 1.7% 0.08% Pyrroles 1.1% 0.05% Thiocyanates traces (i.e. less than 0.05%) Esters traces (i.e. less than 0.05%) Fraction 2 (boiling range: 176.degree.-260.degree. C.) (22.5% of dehydrated sewage sludge-derived oil) Phenols 3.2% 0.7% Pyrroles Esters/acids Succinimide (C.sub.5 H.sub.7 NO.sub.2) Amides traces (i.e. less than 0.05%) Thioureas traces (i.e. less than 0.05%) Thiazoles traces (i.e. less than 0.05%) Fraction 3 (boiling range: 260-400.degree. C.) (30.6% of dehydrated sewage sludge-derived oil) C.sub.n H.sub.2n-1 NO C.sub.n H.sub.2n-1 N. ______________________________________
It was found that, as the fractions get heavier, the identification of individual components becomes more difficult because of the complexity of the fraction.
The actual analysis of this SDO is
N: 6.77% PA0 O: 11.21% PA0 S: 0.74% PA0 H: 9.75% PA0 C: 71.53% PA0 Nitrogen: about 3.4% to about 5.0% PA0 Oxygen: about 5.8% to about 6.9% PA0 Sulphur: about 0.3% to about 0.8% PA0 Hydrogen: about 9.7% to about 10.4% PA0 Carbon: about 76.9% to about 79.8%. PA0 Nitrogen: 6.77% PA0 Oxygen: 11.21% PA0 Sulphur: 0.74% PA0 Hydrogen: 9.75% PA0 Carbon: 71.53%
It has previously been found that the sewage sludge-derived oils have considerable potential as beneficial additives in asphalt. The use of sewage sludge-derived oil for asphalt pavement is disclosed in copending application Ser. Nos. 07/641,861, now abandonded, and 07/641,872, now abandoned, each filed 16 Jan. 1991. Unfortunately, these sewage sludge-derived oils are highly odourific and this would be a deterring factor for this attractive utilization outlet. Therefore, significant odour abatement of these oils would improve their commercial utility.
The reduction of odours of vegetable oils by circulating carbon dioxide through such oils during steam distillation has been achieved by others, in particular, by L. Hartman and Daniela Reimans as described in "Preparation of Medium Chain Glyceride, With Use of Physical Refining" in Fett Wissenshaft and Technologie 1989, 91 (81 p 324).
The patent literature also discloses procedure for removing undesirable materials from organic materials. For example, U.S. Pat. No. 3,977,972 patented Aug. 31, 1976, by H. P. Bloch, provided a method and apparatus for reclaiming contaminated liquid, e.g. seal oil. The procedure provided for the reduction of H.sub.2 S by bubbling gas through it, e.g. nitrogen or air.
U.S. Pat. No. 3,992,285 patented Nov. 16, 1976, by L. E. Hutchins, provided a process for the conversion of hydrocarbonaceus black oil. The patented process involved desulphurization using a steam-containing gas and a desulfurization catalyst.
U.S. Pat. No. 4,406,778 patented Sep. 27, 1983, by M. Borza et al, provided a spent oil recovery process. The patented process involved the extraction and removal of insolubles from the oil using a gas under supercritical conditions.
U.S. Pat. No. 4,522,707 patented Jun. 11, 1985, provided, by E. Kriegel et al, a method for processing used oil. The patented process involved the extraction of used spindle and neutral oils with a gas under supercritical conditions.
U.S. Pat. No. 4,518,489 patented May 21, 1985, by D. O. Hitzman, provided an oil treatment process.
That patent provided a process for treating hydrocarbon oils in order to separate nitrogenous substances, as well as other contaminants. The process included the first step of contacting the oil in the presence of water with an acid gas which has an affinity for nitrogenous substances under specified conditions. The conditions included temperature in the range of about 20.degree. to about 90.degree. C., sufficient pressure and contacting with an immiscible phase, e.g. water, an immiscible solvent or mixtures thereof. This was effective to provide removal of nitrogen-containing compounds. The second step involved separating the immiscible phase containing nitrogen-containing compounds from the hydrocarbon oils. In this way, basic nitrogen-containing compounds were removed from mineral oil, e.g. shale oil, by extraction with an immiscible aqueous phase containing an acid gas, e.g. carbon dioxide. The effectiveness of the separation was proportional to the partial pressure of the gas.
That patentee further taught that organic compositions suitable for treatment by the recited process were any nitrogen-containing compounds, particularly primary, secondary, and tertiary amines and heterocyclic compounds, e.g. pyrrole, pyridine, indole, quinoline, etc., and their derivatives. Oil-based materials which could be treated by that invention included shale oil, petroleum, and liquid products from tar sands and coal and lignite liquefaction.
In view of the above-described technology and patents, there is thus an ever present need for the treatment of various carbonaceous compositions to remove undesirable components therefrom. Many expedients, as above described, have been advanced to treat various oil fractions. Examples of such treatment include the purification of mineral oils and other carbon-containing materials containing undesirable contaminants; the extraction of mineral oils to remove therefrom nitrogen-containing compounds and other impurities by extraction; the use of a CO.sub.2 or other acidic gases as extractants for the removal of contaminants from various organic compositions containing same; and the treatment of oils and other organic compositions containing nitrogen-containing compounds and undesirable contaminants, to render the oils and/or the nitrogen-containing compounds more desirable.
However, none of the above-described compositions is a sewage sludge-derived oil nor are they the art-recognized equivalent thereof. Moreover, the procedures taught are for the removal of nitrogenous compounds and not necessarily for the removal of odouriferous compounds therein.